Specific tests
The August Psychiatric Times article mentioned 3 specific blood tests.1 VeriPsych is a diagnostic test used to confirm the presence of recent-onset schizophrenia on the basis of 51 protein biomarkers. MDDScore is a test that measures 10 biomarkers to help diagnose and manage major depressive disorder (MDD). The Human Metabolome Technologies’ test measures the levels of ethanolamine phosphate in the blood to help in the diagnosis of MDD.
Balt commented, “the ethanolamine phosphate finding is fairly inscrutable, since it still has not been published. Similarly, Ridge Diagnostics’ MDD Score has not been presented in the scientific literature.” Balt noted that the ethanolamine phosphate test failed to identify depression in 18% of the cases and falsely labeled healthy people as “depressed” 5% of time.
“Further,” he said, “what exactly is ethanolamine phosphate, and why would it be low in depressed people? As far as I can tell from a quick literature search, there has been no report—or even a suggestion—of ethanolamine being involved in the pathogenesis of mood disorders.
“Obviously,” he added, “the finding has to be replicated. If it was, in fact, just a lucky result, further research will bear that out.”
In contrast, the VeriPsych test is “more interesting,” Balt told Psychiatric Times. “The data have been published, and it does look like there are some analytes that might correlate specifically with a diagnosis of schizophrenia,” he said. “However, few of their analytes meet all of their selection criteria and many of the proteins are nonspecific and can be altered in other medical conditions.”
Balt contended that it is “absolutely premature for clinicians to order these tests,” because they don’t guide treatment. Rather, he said, “they add to our clinical suspicion about the diagnosis and might distract us from the patient’s actual symptoms and clinical presentation.”
In addition, Balt is concerned about the high cost of the tests.
“The VeriPsych test costs $2500? Why not use that money for therapy, a medication trial, or psychosocial treatment of patients who have actually been diagnosed with schizophrenia?” Balt asked.
Balt is apprehensive about basing the biomarkers on DSM-IV. “The validity of these biomarkers has less to do with their reproducibility and correlation with clinical diagnosis, and more to do with the validity of the diagnoses themselves,” he said.
“The categorical (as opposed to dimensional) diagnoses in DSM-IV give rise to a heterogeneous population of what we call ‘schizophrenia.’ Any good psychiatrist will tell you that there are many types of schizophrenia and depression, so a blood test that can ‘diagnose’ schizophrenia is either a nonspecific measurement of emotional distress (or some such thing) or a stroke of luck. It would be better, in my opinion, to look at subgroups of schizophrenia patients (eg, young versus old, male versus female, paranoid versus grandiose delusions, with or without a history of substance use) and determine markers for those. It would more accurately guide our treatment, and we might learn more about the pathophysiology of specific disease subtypes.”
